MIMO is an abbreviation for Multiple-Input Multiple Output RF devices that have the ability to simultaneously handle multiple RF data inputs and multiple RF data outputs. RF devices that include MIMO capability may use a RF antenna to send and receive more than one communication signal simultaneously. For example, transmitting a WiFi signal using a dual band antenna and receiving a Bluetooth (BT) signal using the same dual band antenna. A 2×2 MIMO architecture may provide two RF paths that use two RF chains with each chain configured for receiving and transmitting a RF signal. A 1×1 MIMO architecture, also called SISO, allows for one RF path with a single RF chain that is capable of transmitting or receiving a RF signal. MIMO systems that use multiple RF antennas can take advantage of multipath effects that result in improved range and capacity due to more reliable signal quality and increased bandwidth.
The MIMO architectures may utilize one or more antennas or a dual band antenna to transmit and receive RF signals. Those antennas are typically optimized for the intended RF bands the MIMO will be in communications with, such as WiFi (2.4 GHz, 5 GHz) and Bluetooth, for example. However, some systems that incorporate a MIMO architecture may include features that requires an antenna optimized for another function, such as near field proximity detection. In some applications, the antenna to be used for near field proximity detection may be subject to design constraints such as imposed by industrial design considerations (e.g., esthetic requirements), chassis/enclosure design, just to name a few. In other applications, the antenna to be used for near field proximity detection may be configured to not be optimized for any of the frequency bands used by the MIMO. For example, it may be desirable to have an intentionally detuned antenna for antenna for near field proximity detection because it will be less sensitive to signal strength (e.g., RSSI) generated by transmitting devices in the far field region (e.g., >0.5 meters from the antenna) and more sensitive to transmitting devices that are in the near field or very near field (e.g., <0.5 meters from the antenna) or are in direct contact with the antenna. Therefore an antenna that is detuned and/or not optimized for RF bands such as those used for WiFi or Bluetooth, may be desirable for some applications that also include a MIMO architecture.
Thus, there is a need for a RF architecture that takes advantage of MIMO while also incorporating antennas optimized for near field proximity detection into the MIMO architecture while maintaining the advantages of the MIMO architecture.